Profiled tubes or tube segments are made, for example, in the automotive industry for use as sliding pieces for articulated shafts or movable steering columns. As a rule, two tubes are always used, which can slide lengthwise relative to each other, being form-fitted together in regard to rotation about their lengthwise axis. In this way, it is possible to compensate for changes in the interval between the end points of these tubes, while at the same time transmitting a precise rotation. These requirements, as already mentioned, are necessary for both the drive train and the steering in motor vehicles. At the same time, these tubes need to have the lightest possible construction, having a precise profiling with the slightest possible free play, and high strength.
In order to cold-form such thin-walled metal tube segments, being profiled on the inside or outside and having an interlocking profile, one traditionally uses an equally profiled mandrel. This mandrel is introduced into a tube blank and the surface of the blank is worked on mechanically from the outside, for example in the form of impact rollers. This is generally done automatically in a suitably configured production machine. The mandrel needs to have a greater length than the region of the blank being worked on, since the mandrel for the profiling has to remain inserted within the entire length of the blank and then needs to be retracted into the production machine in order to remove the finished workpiece and load a new blank into the production machine.
Thus, this traditional method and the corresponding production machines are only suitable for making tubes of a limited length. If longer tubes need to be made, these production machines reach their limits on account of their dimensions, especially since the mandrel cannot be made arbitrarily longer, due to the higher production costs.